The invention is directed to a system and method for the repair of damaged tissue and bones, congenitally missing tissue/cosmetic and non-cosmetic reconstruction and/or augmentation of tissue, and more particular to an implant having a porous layered structure with sufficiently large exposed pores to promote neo-vascularization as well as bone and tissue formation. This porous implant system can also contain bioactive agents necessary for rapid tissue formation and keep ingrowth of unwanted tissue out of the implant surgical site.
Bone regeneration and generation of new tissue have become important areas in the treatment of various diseases and in reconstructive surgery. Bone grafts can be used to promote healing of fractures and trauma, to promote osteogenesis, for example, following osteomyelitis, and to augment bone in plastic and reconstructive surgery. Other bone diseases are bone diseases resulting in bone loss are periodontal diseases and osteoporosis. Bone repair materials, therefore, are actively sought for bone repair and regeneration. Biodegradable and biocompatible polymeric compositions are useful for bone grafting, bone repair, bone replacement, or bone-implant fixation purposes.
In periodontal reconstruction or implant fixation, bone graft material must support the structural integrity of the site throughout the course of new bone regeneration. Autografts and allografts are used in current bone graft procedures. Autografts are preferable, but are not always available in sufficient quantities or may not produce a clinically desired result. Bone replacement materials for maxillofacial, alveolar and mandibular reconstruction are in use as alternatives to autografts. Clinically applied techniques include the use of biodegradable membranes for guided tissue regeneration during bone recovery after grafting procedures. However, despite significant advances in the development of these technologies to better approximate the three-dimensional nature of complex tissue equivalents, the development of clinically applicable bone replacement materials has remained a challenge. At least in part, the challenge lies with the difficulty in enabling sufficient ingrowth of repair tissues into biodegradable repair materials for prolonged periods of time to allow the bone architecture to form at the defect site. Implantation of such materials in skeletal repair sites commonly produces new bone growth that is often limited to the periphery of the implant rather than an actual tissue penetration throughout the implant. However, tissue penetration appears eminently important for the successful development and manufacturing of universal tissue equivalents for maxillofacial and periodontal applications.
In past approaches, bio-ceramic fillers have been used to provide the desired mechanical strength and structural integrity of bone reconstruction materials. For example, Ca10(PO4)6(OH)2, hydroxyapatite (HA), is a widely-utilized bio-ceramic material for bone repair because it closely resembles native tooth and bone crystal structure. However, sintered HA, while adequate for coatings on porous metal surfaces, tends to be too dense to permit efficient ingrowth of bone.
In one prior art approach, a bioresorbable composition for bone reconstruction was produced from a bioresorbable polymer, a micro- or nano-sized biocompatible filler, and a substance aiding in the creation of pores in the composition. The filler can be HA, the bioresorbable polymer can be a material cross-linkable with a cross-linking monomer, and the pore creating substance can be an effervescent agent such as a carbonate and an acid. However, the pores tend to be isolated, i.e. unconnected, which makes it difficult or impossible for the blood vessels to grow into the composite to a significant depth.
In another prior art approach, a granular material, such as HA, was at least partially embedded in a resorbable polymer film. It was proposed to produce an implant piece in preferably cylindrical form from a cartilage substitute previously. This approach leaves only the ends of the rolled-up sheet exposed for the ingrowth of blood vessels, at least before the polymer film is resorbed in the body.
It would therefore be desirable to provide an implant structure for the regeneration of bone and the generation of tissue with a larger porous surface area and sufficient large pores sizes to permit efficient ingrowth of blood vessels.
It would also be desirable to provide an implant structure with long-term dimensional stability and sized to conform to the size and shape of various implant sites in the body.
It would moreover be desirable to controllably supply and time release as part of the implant structure therapeutic, analgesic and/or antibacterial substances, growth factors, proteins, peptides, drugs, tissue subcomponents including but not limited to bone particles and hydroxy appetite, which promote growth, prevent infections and the like. The bone particles can be autografts, allografts, xenografts (usually bovine) or alloplastic bone grafts (synthetic, such as β-tricalcium phosphate).
It would also be desirable to provide an implant suitable for the generation and/or regeneration of soft tissue, depending on the type of tissue desired.
It would be desirable also to have an implant suitable to permit in growth of blood vessels yet keep unwanted tissue from growing into the surgically placed implant during healing.